Randomization is key to many ways of playing Raid Format successfully, and often includes a dice roll. Some ways of randomizing choices are below:
Binary Choice
Use heads or tails, which is often evens for heads, or odds for tails. Alternatively, when selecting a Pokémon attack, 1-3 could be the first attack, and 4-6 the second attack.
Three Choices
When a choice must be made between three choices, assign them logical numbers, and identify these to the Players.

Four or More Choices
Consider the case of a VMAX Raid Boss with Technical Machine: Evolution attached. In this case, there could be up to four attacks that would need to be randomized. In this case, clearly identify to the Players which attacks correspond with which die rolls, and roll accordingly.
